Receivers are well-known components for communication systems. A receiver may include a low noise amplifier (LNA) for filtering inbound radio frequency (RF) signals, and mixers for generating intermediate frequency (IF) signals by mixing the filtered RF signals with a signal from a local oscillator.
The IF signals may be filtered by a bandpass filter (BPF). The frequency band of the BPF needs to be accurately tuned to the desirable frequency band to ensure good performance of the respective receiver. However, due to the process variation and temperature variation of the BPF, the frequency band may have big variations, and hence the BPF needs to be calibrated.
Conventionally, the BPF may be calibrated through the calibration of the resistors and/or capacitors in the BPF. The BPF were calibrated using an external calibration system external to a capacitor bank (array) of the BPF, and a capacitor bank of the external tuning system is calibrated, and the capacitor code for calibrating the capacitor array of the external tuning system is latched to the capacitor bank in the BPF, and hence the capacitor bank in the BPF is also calibrated.
When the scale of the integrated circuits becomes smaller, there is an increasingly greater intra-die mismatch between the capacitor bank of the BPF and the capacitor bank of the external tuning system even if they are on a same die. The accuracy in the calibration is thus impaired. Further, the external tuning system requires extra chip area.